Which way will technology take us?

Radical Evolution: The Promise and Peril of Enhancing Our Minds, Our Bodies  and What It Means to Be HumanBy Joel GarreauDoubleday, 400 pp., $26

We'll eat whatever we want but never get fat. Real estate will be virtual. Cheap, tiny computers will be smarter than we are. Energy demands will be met by nanoscale renewable technologies. We'll choose when, and if, we'll die. Many organs will be irrelevant, we'll be able to select from alternate personalities, and those among us who are ''software-based" will be a decade or two away from being ''able to expand [our] thinking without limit."

Is this utopia? A new science fiction movie? An optimistic scenario for human life in the year 2500?

Try 2030. It is a prediction evangelized in intense detail by Ray Kurzweil in his staggering new 650-plus-page treatise, ''The Singularity Is Near." Kurzweil, a renowned computer scientist and inventor of, among other things, the flatbed scanner, argues that our society is facing an imminent and overwhelming transformation called the Singularity.

The Singularity is, in Kurzweil's words, ''a future period during which the pace of technological change will be so rapid, its impact so deep, that human life will be irreversibly transformed." Another way to put it is to say that pretty soon biological evolution will be transcended by technological evolution.

Too wild? Before you dismiss it as techno-zeal, think for a moment about what is going on in 2005; think about the kind of things that are written about on the other pages of this newspaper. Breast exams are performed by robotic hands. Refrigerator magnets (or car keys, or hearing aids) contain chips that match the computing power of PCs we happily spent a couple of thousand dollars on in 1990. Our soldiers have X-ray, night, and telescopic vision. Computers launch, fly, and land supersonic airplanes.

Every day the line between what is human and what is not quite human blurs a bit more. We are, in many ways, already engineering our own evolution. Consider Viagra, steroids, or in vitro fertility treatments. Is it really so improbable that someday soon high schoolers might be able to access the Internet through an implant in their brain? Or that robots the size of red blood cells will be injected into our bloodstream to repair diseased organs?

What Kurzweil assumes is that (1) technology drives history and (2) technology (and therefore order and complexity) will continue to advance at an exponential rate.

Exponential curves are the kind of curves that get very steep very quickly. Put time (1980, 1990, 2000) on a horizontal axis, and the growth of information technology -- say, the speed of Intel's microprocessors -- on a vertical axis. Then project the curve into the future. Toward the right side of the graph, the steep end, the pace begins to double with deceptive rapidity.

Or think of it this way. Imagine your son talks you into doubling his allowance every day for a month. Start him at a dollar. By the fifth day you'll owe him 16 bucks. By the end of 30 days, want to know what he'll be holding out his hands for? $1,073,741,823.

Kurzweil's book is surprisingly elaborate, smart, and persuasive. He writes clean, methodical sentences, includes humorous dialogues with characters in the future and past, and uses graphs that are almost always accessible. Of course, he also swallows ''250 supplements (pills) a day," declares that ''we have the means right now to live long enough to live forever," and is certainly quirky.

For a broader survey of predictions about the future of our species, you might try Joel Garreau's ''Radical Evolution."

Garreau covers Kurzweil in all his splendor, but also gives voice to the Singularity's mirror image, a scenario Garreau calls Hell. Hell is genetically altered viruses unleashing plagues across continents. Hell is warfare between altered humans and natural ones, or billions of infinitesimal, self-reproducing robots transforming all matter -- including us -- into a gray pudding. Levelheaded, hugely intelligent people, like Bill Joy, the longtime chief scientist at Sun Microsystems, or Martin Rees, the astronomer royal of the United Kingdom, subscribe to the likelihood of catastrophic futures like these.

Garreau also devotes plenty of pages to a more toned-down range of scenarios he calls Prevail. The advance of technology, proponents of this scenario argue, does not necessarily match the messy, hiccupping curve of history.

Futurists, like prophets, tap into our insatiable interest in utopia and dystopia. We crack open fortune cookies; we peer into the lines of our palms. You read Kurzweil and think of George Orwell, Aldous Huxley, Mary Shelley, or H. G. Wells.

There will always be an unpredictability to our destiny, no matter how much logic we apply to projections. But it is impossible to disagree that we live in a time when change happens with breathtaking speed.

So before we dismiss Kurzweil's Singularity, we should remember that what sounds wildly ridiculous to a population one year is often commonly accepted a few years later. In 1845 no Americans wore garments made by machinery. A decade later thousands did. In 1913 the founder of RCA was prosecuted by the US government for claiming the human voice could be broadcast over the Atlantic Ocean. World War II was ended with technology that didn't exist when the war began.

Kurzweil might be hugely optimistic, and he might be proven wrong, but at least he's aiming his telescope at the horizon, and trying to fit his mind around what he sees.

Anthony Doerr is the author of ''The Shell Collector" and ''About Grace." See ''Bookings," Page D8, for information on a local appearance by him.